1. Field of Industrial Applications
This invention relates to a method for producing a bonded body of silicon nitride ceramics having a continuous, homogeneous structure.
2. Prior Art
Heretofore, bonded bodies of silicon nitride ceramics have been produced by fusion-bonding using a glass, metal and the like which is different from ceramics. However, the bonded body having such dissimilar phase in the bonded area suffers low thermal shock resistance and creep characteristics. Thus, the bonded body does not meet a condition of the ceramics, that is, the ceramics has high thermal resistance.
Silicon nitride ceramics bodies can be bonded together by sintering them with silicon nitride ceramics powder interposed between the bonding surfaces thereof. However, sufficient bonding strength cannot be obtained because silicon nitride is difficult to sinter. On the other hand, it is possible to produce a bonded body containing no dissimilar phase and having a high bond strength by using the hot press method which produces a synergistic effect of mechanical pressure and high reaction temperature. Unfortunately, the hot press method is not suitable for bonding objects of complex shape and is not economically advantageous.
Since a dissimilar phase between the bonding surfaces of silicon nitride ceramics makes the bonded body thermally unstable as mentioned above, it is desirable that the bonding interface has the same material as the bonding surface and the bonded body has a continuous, homogeneous structure. In the case of silicon nitride ceramics, there has been no way of producing such a bonded body having high bond strength without resorting to the hot press method.